1. Field of the Invention
The present invention generally relates to a vibration absorbing device, and, more particularly, to an annular mass which is attached to the inside surface of a tubular structure, such as an impeller.
2. Description of the Prior Art
Whenever a rotatable device is driven by a source of motive power, such as an internal combustion engine, there are many possible sources of vibration that can cause noise at certain frequencies. For example, if the rotatable device, such as an impeller for a marine propulsion system, is connected to the source of motive power by shafts, splines, and gears, variations in torque transmitted from the source of motive power to the rotatable object can cause vibration and noise. Those skilled in the art are familiar with many techniques that can be used to dampen vibration and reduce noise.
U.S. Pat. No. 4,884,666, which issued to Stahl on Dec. 5, 1989, discloses a torsional damper and mounting adapter. The assembly for dampening shaft vibration and noise comprises an annular torsional damper which is fixedly mounted to a cylindrical flange of a mounting adapter. The opposite ends of the adapter are cylindrically shaped and extend into adjacent ends of a pair of shafts which are affixed thereto.
U.S. Pat. No. 5,231,893, which issued to Sisco et al on Aug. 3, 1993, describes a dual mode damper. The crankshaft vibration damper is provided with a unique elastomer member that is positioned between a hub and an outer annular inertia member. The hub is configured for connection to the accessory drive end of the crankshaft. The inertia member may or may not be grooved to accept an accessory drive belt. The resilient elastomer member is dimensionally and chemically developed to dampen torsional and bending vibrations when assembled between a corresponding curved hub and inertia member. The radically outward or inward curvature of the hub and inertia member is selected to be sufficient to effectively reduce crankshaft bending vibration.
U.S. Pat. No. 4,905,956, which issued to Zemlicka et al on Mar. 6, 1990, discloses a fluid mounting system for a marine engine. The mounting system includes a combination of a solid elastomer and a fluid dampening means to significantly improve vibration isolation and cushioning under normal shock loads. The fluid dampening means is constructed to lock up and become inoperative under heavy shock loads to protect the mount against overload failure. An improved mounting system utilizing the fluid mounts optimizes the performance thereof.
U.S. Pat. No. 4,200,004, which issued to Bremer on Apr. 29, 1980, discloses a zero slip torsional vibration damper. The damper has an inertia ring coupled to a hub by means of an elastomer member. The hub is attached to a shaft which is subject to torsional vibrations. The radically outermost portion of the elastomer carries angularly spaced pockets into which a damper liquid of high viscosity is placed. The specific improvement of this device resides in thickening the radically innermost portion of the elastomer, relative to the radically outerpost portion. In assembling the damper, the radically innermost elastomer portions are compressed while the portions of lesser thickness are not compressed. A thin film of viscous liquid is adjacent the elastomer portions of lesser thickness and thus functions as a viscous damper while the thicker elastomer portions function to elastically dampen torsional vibrations.
U.S. Pat. No. 5,095,786, which issued to Bellinghausen et al, on Mar. 17, 1992, describes a method in apparatus for dampening brake lathe vibration. The device is directed to a brake lathe having a device to eliminate or reduce vibration. Various types of dampers can be mounted on an arbor shaft of the lathe.
U.S. Pat. No. 4,962,677, which issued to Withers on Oct. 16, 1990, describes a harmonic balancer. A torsional vibration damper is used to dampen harmonic vibration frequencies set up in crankshafts of reciprocating internal combustion engines. The balancer has a hub section to be fitted to the crankshaft requiring balancing. The hub section defines an outwardly directed peripheral phase which has an annular ring of elastomeric material received thereover. The balancer also has an inertial ring press fitted over the elastomeric material ring with an inwardly directed phase of the inertia ring engaging the elastomeric material. The inertia ring includes an inwardly directed member which is located at one axial end of the inertia ring and has a free end located at a radial distance from the axis of rotation of the shaft being balanced less than the radial distance of the peripheral face of the hub section from the axis of rotation. It also includes a plastically deformable member that is located at the other axial end of the inertia ring. The deformable member has a free end in an undeformed state spaced from the axis of rotation a distance no less than the radial distance between the axis of rotation and an outer surface of the elastomeric material. The free end of the deformable member is located, in a deformed state, at a radial distance from the axis of rotation which is less than the radial distance of the peripheral face of the hub section from the axis of rotation of the balancer.
U.S. Pat. No. 4,590,856, which issued to Mamberer et al on May 27, 1986, discloses a lifter-type inker for rotary printing machines including rotational shock dampening means. In order to prevent printing of an imperfect copy by a printing machine having a lifter-type inker, which is caused by cyclically recurring rotary oscillations or vibrations, the breaking torque introduced upon contact of a lifter roller with a first milling and distribution roller of the inker is prevented from propagating through the gearing drive of the respective ink rollers. To prevent such propagation, the first milling and distributing roller is yieldingly driven at machine speed, for example by a frictional drive, transmitted through an elastic surface of a soft roller in frictional drive engagement with the first milling and distributing roller as well as a positively driven subsequent milling and distributing roller, or a circumferencially resilient yielding coupling, is interposed between the driveshaft element for the first milling and distributing roller and a positive gear drive. Preferably, the inertia of the first milling and distributing roller is high with respect to that of the lift roller and is, for example, enhanced by a flywheel.
U.S. Pat. No. 4,044,628, which issued to Jacks on Aug. 30, 1977, discloses a torsional damper for reducing the vibrations produced when a shaft is driven by the intermittent application of a discontinuous force thereto. An example of this application is the crankshaft of an internal combustion engine. The damper comprises an integrally formed disc-like mass having three concentric zones, namely an inner central zone, an outer annular zone, and an intermediate spring zone there between. The spring zone includes narrow, elongated, spirally arranged, overlapping slots extending axially through the disc and radically between the inner and outer zones to provide spirally arranged overlapping webbed portions which act as torsional springs or shock absorbers due to an inherent resiliency. The spirally slotted damper is formed as an integral unit by casting it from a metal such as cast iron, with spiral slots having a predetermined size and shape to provide the desired damping effect.
In certain applications of rotating equipment, it is difficult to provide sufficient space for a damper to reduce vibration and noise transmitted from an internal combustion engine to a rotatable object, such as an impeller of a marine drive system. Spatial restrictions often inhibit the use of known vibration dampening means attached to the crankshaft of the internal combustion engine or the driveshaft of the impeller. It would therefore would be significantly beneficial if a means could be provided to dampen the vibration and noise transmitted to an impeller of a marine drive system without requiring space to be diverted to the torsional dampening system.